One state-of-the-art intrauterine device (cf. GB, B, No. 1,456,46) is known to be made as a T-shaped element, comprising a rod and two elastic arms branching off radially therefrom, and an elastic loop provided at its end. The arms are equally curved, the radius of curvature of each arm being adequately large, while the angle between the rod and each of the arms is less than 90 degrees.
The prior-art device is characterized by the fact that an inadequately intimate contact between the arms of the device and the mucous membrane of the uterine fundus effects adversely the contraceptive effect, while insufficient elasticity and size of the loop are liable to inflict trauma and irritate the mucosa of the internal uterine orifice and hence spontaneous expulsion of the device.
Another prior-art intrauterine device, i.e. Nova T Cu200Ag (A/O Huhtamaki, Leiras, Finland) is known to comprise a rod with a copper coil, a strip with the rounded-off ends, held to the rod so as form a T-shaped element therewith, and a fixing element to retain the entire device within the uterine cavity, said fixing element being in fact an elastic loop located at the rod end.
The aforesaid prior-art device is characterized by the fact that provision of the elastic loop at the rod end, the loop size and shape fail to provide constant pressing of the strip against the mucous membrane of the uterine fundus, which is the cause of impaired contraceptive effect. On the other hand the base of the elastic loop irritates the receptors of the mucosa in the region of the internal uterine orifice, provokes extraordinary contractions of the uterine muscle and promotes expulsion of the entire device.
In addition, the devices discussed above should have various sizes and shapes to suite the various sizes and shapes of the uterine cavity.